Connecting-cibctjit eob telephone systems



R, L. QUASS. CONNECTING CIRCUIT FOR TELEPHONE SYSTEMS.

APPLICATION FILED JULY 19. l9l7 Patented May 20, 1919.

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R. L. QUASS CONNECTING CIRCUIT FOR TELEPHONE SYSTEMS.

APPLICATION FiLED 1ULY1 9| 191?.

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RALPH-L. QUASS, 0F HAWTHORNE, NEW JERSEY, ASSIG-NOR T0 WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK. N. Y., A CORPORATION OF NEW YORK.

CONNECTING-CIRCUIT FOR TELEPHONE SYSTEMS.

1,30a,9eo.

Specification of Letters Patent.

Patented May .20, 1919.

Application filed July 19, 1917, Serial No. 181,575. v

To all whom it may concern:

Be it known that I, RALPH L.. 'QUASS, a

citizen of the United States, residing at Hawthorne, in the county of Passalc and which the following is a full, clear, concise, and exact description.

This invention relates to a connecting 01rcuit for telephone systems, and more par;

ticularly to a circuit which may be used to supplement the connecting circuits of a call distributing system or may be used independently as an A operators cord circuit.

In call distributing systems it is customary to provide apparatus which operates automatically to extend the circuit of a calling line to any one of a number of operators positions that is at the time available,

.and to provide each operator with means for extending theconnection of the calling line to 21 called line, as by inserting into a spring-jack of the called line the plug of the connecting cord to which the calling line has been extended. In the operation of such systems, it sometimes happens that it is, desirable 'for the operator to have means for establishing connection between the calling and the called line independently of the call distributing connecting circuit over which the call has reached her; as, for instance, when the normally-established connection is accidentally interrupted, or when the normany-established connection is noisy and request is made for another connection, or when the called line is busy or does not answer and the request is made that an attempt bemade to establish the connection later, or

when other connections of an extraordinary nature are to be made. The particular object of this invention is to prov de a connecting circuit having the special characteristics that will enable the operator to meet these and other special service conditions, and

which also will be adapted for use in answering calls and establishing connections in the ordinary way. a a v The preferred embodiment of the invention is shown in the accompanying drawing, in which Figure 1 illustrates diagrammatk cally two telephone lines with the associated apparatus at the subscribers statlons and the central oflice, and indicates circuits and apparatus over which calls from these lines normally reach an operators position; and Fig. 2 illustrates the circuits and apparatus at an operators position, including the call distributing connecting circuits for normally completing connection, and the special connecting clrcuit over which the operator is enabled to establish alternative connection with the calling and called subscribers lines.

As indicated in the drawing, the organization over which the calling subscribers line is normally extended to the operators position may comprise a finder circuit F terminating at one end in the brushes of a switch LF through which the finder circuit is brought into connection with the terminals of the calling line, and at the other end in the brushes of a switch CS by means of which the finder circuit may be brought into connection with the terminals of an available connecting circuit terminating in the plug 170 at the operators position.

It will be sufficient merely to outline the manner in which a connection is established between a calling subscribers line and a called subscribers line in the normal operation'of the system, for the reason that the invention is particularly concerned with the special cord circuit, and the normal mode of establishing connection has only an inci- 11.- The line relay in operatmg may bring about the operation of the line finder switch LF, in a manner that need not here be described, toextend the circuit of the calling lineto the conductors of the finder circuit F or to the conductors of a similar finder circuit the provision of which is indicated by the switch brushes LF' and CS. The extension of the calling line to the finder circuit F brings about the operation of the associated cord selector switch OS to further extend the circuit of the calling line tothecordcircuit C. When this occurs the operators, telephone apparatus 147 may be brought into connection with the cord circuit C by the operation of the switches 308, 309, 310 and 311 under the control of a to the part tion of the conversation, the

sequence switch motor magnet 300. The movement of these switches into their alternate position breaks the continuity of the cord circuit, and reestablishes the circuit by way of that portion of the operators telephone circuit which includes the ring-back key 160. The operation of the key 160, when occasion arises, interrupts the continuity oi the cord circuit and applies ringing current from the ringing generator 63 of the circuit which extends back to the calling subscribers line.

.When the operators telephone set 147 is brought into connection with the calling subscribers line in the manner described, the operator is enabled to inquire and be informed of the number of the line with which connection is desired. When the operator has obtained this information, she tests the called line by touching the tip of the plug 170 to the sleeve of the called line springqack, as 1st, and, if the line is not in use, establishes connection by inserting the plug. When the plug is inserted, ringing current is applied to the called line by moving the switches518 and 519 to engage their alternate contacts. This applies ringing current from the generator 181 and rings the bell at the called subscribers station. The line relay of the called line has in the meantime been disconnected from the line by the. operation of the associated cut-oft relay 1]., this relay being energized by the circuit established from battery through the winding of the relay 175, sleeve of the calling plug 170 and corresponding contact of "the called-dine spring-jack, and the winding of the cutoff relay 11' to ground. The energization of the relay 175 disconnects the tip of the calling plug from the test conductor 133 and connects it with the tip strand of the connecting circuit. When the called subscriber responds, the talking circuit between the calling and called stations is completed through the repeating coil 169 interposed in the usual manner in the talking conductors of the cord circuit. The supervision of the connection may be controlled in the usual manner through the medium of the answering supervisory relay 171 and the calling supervisory relay 187. While the connection is established the contacts of the switch 15:2 are closed. Upon the terminalug 170 is withdrawn and the contacts oi the switch 152 are opened. When this occurs, the circuit is broken that had previously existed from battery by way of resistance 155, closed contacts of the switch 152, closed contacts of the switch 217 of the finder circuit, the winding of the finder circuit relay 230, closed contacts 212, finder circuit conductor and line conductor 53, and winding of the cuto'li relay 11 to ground. The opening of this circuit releases the cut-ofi relay 11 and the incense scribed in outline in the foregoing, reference had to an application to S. B. Wilmay be 107,090 filed July 1,

liams, Jr., (Serialhlo. 1916).

The sequence switches that will be referred to in the description that follows may be of the type disclosed in Patent 1,127,808 issued February 9, 1915, to Reynolds and Baldwin. Each consists 01. an electromag netically controlled motor or driving mechanism and a number of associated switch cams. The cams associated with the sequence switch 400 are designated 401 to 111 inclusive; those associated with the sequence switch 500 are designated 501 to 510 inclusive. To each of the contacts associated with the various sequence switch cams are applied certain numerals. These numerals in the case of the cams 101 and 501 indicate the only positions of the associated sequence switch in which these particular contacts are open; the numerals applied to all the other contacts of each sequence switch indicate the only positions of the particular associated switch in which the corresponding contacts are closed.

in order to convey an understanding of the organization and mode of operation of' the special connecting cord circuit one of the special conditions under which that cord circuit is used will now be assumed. The condition that will be assumed is that a call has reached the operators position by way of the call distributing apparatus and the regular cord circuit C, and that when the operator attempts to take the order from the subscriber, she finds the connection noisy, presumably due to some trouble in the connecting circuit. In this case, the operator, instead oi attempting to complete the establishment'ot the connection by inserting the calling plug 170 of the regular connecting circuit C in the spring-jack of the called subscribers line, inquires the number of the calling subscriber and proceeds to establish the connection by means of a special connectin circuit 5.

Having learned the number of the ca ing subscribers line, the operator picks up he answering plug 31 of the special connecting circuit Snnd inserts the plug in the multiple spring-jack 11 of that line, it being assumed that the calling line is-the one represented as extendingctrom station A. At the same time the switch 159, of the regular connecting circuit C is operated to open its contacts, as a'result of which the finder circuit F is disconnected from the calling subscriber-s inc line and from the regular connecting circuit C and the circuits F and C are returnedto normal. 1

In inserting the answering plug 31 of the special connecting circuit in the multiple spring-j 14, the tip of the plug first touches the thimble or sleeve of the spring.- jack. This; completes a circuit that pro duces a click in the operators telephone re ceiver which serves as a partial check upon the correctness of the connection, as the line that is. being connected with at the time not yet become disconnected fromthe linefinder switch LF over which the call was first transmitted to the operator, and therefore has a; potential on the conductor connected with the sleeve of the spring-jack 14. This potential causes a flow of current by way of the tip of the plug 31, left-hand armature and back contact of relay 41, and winding of relay 35 of the operators telephone apparatus to ground. The relay. 35 is energized and closes a circuit that extends from battery through the winding of the retardationcoil 36, front contact and armature of relay 35, and test winding of the operators induction coil 146 to ground, thus producing a click in the operators telephone receiver.

When the answering plug 31 is fully inserted 'in the spring-jack 14, a circuit is closed that extends from battery through the winding of the relay 41, winding of relay 45, corresponding sleeve contacts of the answering plug 31 and spring-jack 14, and winding ofthe cut-0d relay 11 of the calling subscribers line to ground. The completion of this circuit continues the energization-- of the cut-oil relay 11 to keep the linelrelay 12 disconnected from the calling subscribers line, and also operates the relays 41- and 45 of the special connecting circuit. The relay 41 in operating disconnects the tip of the answering plug from the test conductor and connects through to the corresponding talking conductor of the connecting circuit. The relay 45 in pperating closes a circuit that extends from battery, through the resistance 46, answering supervisory lamp 47 and left-hand front contact and armature of relay 45 to ground. But the answering supervisory lamp 47 remains dark, as the energization of the'answering supervisory relay 51, when the answering plug 31 was inserted, has closed about it the shunt path including the resistance 52. In operating, relay 45 also closes, a circuit that extends from battery through the left-hand winding of the relay 42, right-hand back contact and armature of relay 40, and right-hand front contact and armature of relay 45 to ground. Belay 42 in operating closes a circuit that extends from battery through the motor magnet and contact 402 (1) of listening sequence switch 400, inner front Contact and quence switch 300 of the connecting circuit C. Sequence switch 300 moves out of the listening position in which it has been standing up to this time and in so doing opens the circuit of a relay 161 which in turn allows the switch contact 152 to open. This causes the restoration of switches'LF and CS and cord circuit C in the manner fully described in detail in the above mentioned application to Williams, Serial No. 107 ,090.

In movlng to position 7, the listening-key sequence switch closes a circuit that extends I from battery, through resistance coil 54, calling signal lamp 55, ringing sequence switch contacts 504 (1 to. 2), listening sequence switch contacts 405 (2 to 7), and calling signal interrupter 56 to ground. The result of the closure of this circuit is to cause an intermittent display or flashing of the lamp 55 that continues while the sequence switch 400 is in its listening-in position and until the calling plug 32 is inserted. The movement of the listening key sequence switch to position 7 also operates the listening key sequence switch cams 408, 409, 410 and 411 to interrupt, at contacts 408 8 to 6) and 409 (8 to 6),t'he through circuit of the talking conductors of the connecting-cord and to connect at the contacts (6 to 8) of the cams 408, 409, 410 and 411, a loop extending to the operators telephone set and including the ring-back key 160. As a result of the closure of this loop circuit, the operators telephone set is connected with the special connecting circuit S by way of the resting contacts of the relay 57 and the cams 408, 409,410 and 411 of the listening key sequence switch. I

The operator is thus automatically brought 111139 communication with the calling subscriber by wayof the answering cordof the special connecting circuit that has been substltuted for the re llar circuit C, and by speaking to the cal mg subscriber is able to verify the fact that he is the one whose call reached her a moment before by way of the regular connecting circuit C. Having ascertained this fact and being informed of the number of the line to which thecalling subscriber wishes to be connected, the operator tests the multiple spring-jack of that line, and, if the line is free, completes connection all armature and back contact of relay 33 and the winding of relay 35 otthe operators telephone apparatus to ground, and the energization of the relay 35, in case the called line is busy, causes a click in the operator s telephone receiver in the same manner as has already been described in connection with the test made by the answering plug; 31. TV hen the calling plug 32 is fully inserted in the spring jack it, a circuit is completed that extends from battery, through the windings of the relays 37 and 33 in series, the cooperating sleeve contacts of the calling plug 32 and the called line spring-jack 14:, and the winding of the cut-off relay ll of the called line to ground. The cut-off relay 11 acts to disconnect the associated line rolay 12 in the usual way. The relay 3% in operating disconnects the tip of the calling plug 32 from the test relay 35 and connects it instead with the tip strand of the connecting circuit. The relay 33 in operating also closes a Circuit that extends from battery through the left-hand winding oi the relay l-Q and the right-hand trout contact and armature of the relay 33 to ground, This circuit is a maintaining circuit for the relay 422, which. relay, as has been described, was operated when the answering plug 31 was inserted. The relay 42, therefore, after being energized by the insertion of the answering plug, is held energized as long as either the answering plug 31 or the calling plug 32 is inserted in a spring-jack, and thus a path to ground is maintained by way of the contact ace (1) of the listening sequence switch for preventing the listening key sequence switch from stopping in position 1 as long; as either plug is inserted after the relay t2 has been initially energized,

VI hen relay 37 operates, as a result of the insertion of the calling plug; 32, it closes a circuit that extends from battery through the motor magnet and contact 502 (1) of the ringing sequence switch 500, right-hand front contact and armature of relay ll (which relay is operated as a result of the calling plug being inserted) and the right hand trout contact and armature oi rela 37 to ground, As a result of the closure oi this circuit the sequence switch 500 moves out of position 1 and stops in position 2. This closes a circuit that attends from tery through the winding of the motor map; not and contact 403 (7) oi? the listening sequence switch, righthand hack contact and armature of relay as and ringing sequence switch contacts 505 (2) to ground. a i licit thi circuit is closed, the listening hey se quence switch e00 moves out of position 7 and comes to rest in position 15, its listening-out position. When the listening se quence switch reaches position 8, it closes a circuit that extends from battery through the motor magnet and contact 503 (2) of the ringing; sequence switch, and contacts 406 (8 to 15) of the listening sequence switch to ground. The closure of this circuit moves the ringing sequence switch out of position 2, and it continues to move until it reaches position 13. The listening sequence switch in moving out of position 'i' operates the cams 408, 4-09, 410 and all. to-disconnect the operators telephone apparatus and complete the direct connection of the talking strands of the connecting circuit it also opens at contact 405 (2 to 7), the circuit from the lamp 55 to the calling; signal interrupter 56; and the ringing sequence switch, when it reaches position 3, completes the circuit oi the lamp 55 directly to ground by way of contact 504- (3 to l6) of that se quence switch. Therefore, the flashing ot' the lamp 55 is changed. to a steady glow.

. The calling supervisory lamp is displayed as soon as the calling plug is inserted, the circuit that causes the illumination. of the lamp extending from battery by way of resistance 59, lamp 58, ringing sequence switch contact 506 (1 to 17) and left-hand armature and front contact of relay 3? to ground.

When the ringing sequence switch 500 reaches position 12, a circuit is closed that extends from battery, by way of the winding of relay 60, left-hand armature and back contact of relay 61, back contact and armature, of relay 62, ringing sequence switch contacts 507 (12 to 13), ringing sequence switch contact 508 (3 to 13), right-hand front contact and armature of relay 4:1 and right-hand front contact and armature of relay 37 to ground. As long as the armatures of relay 60 are unattracted, a circuit exists by way of the right-hand back contact and armature of relay 60 and contact 503 (d to 13) for continuing the movement of the ringing-key sequence switch, When,

therefore, relay 60 is operated by the closure of its energizing circuit, as traced, upon the ringing sequence switch reaching position. 12, the energizing circuit of the ringing sequence switch motor magnet is opened at the right-hand back contact and. armature of relay 60 and the sequence switch comes to rest in position 13.

In position 18 oi the ringing sequence switch acircuit is closed for applying ring, ing current to the called subscrihcrs line, This circuit extends from the ringing gen erator 53 by way oi the commutator l3,

which acts to connect the generator and battery alternately with. the circuit, ringing sequence switch contact 509 (13), winding of relay 62, left-hand armature and trout contact of relay -60, ringing sequence switch contact 511 (13), ring contact of the calling plug 32 and corresponding switch spring of the spring-jack l4, and thence over the associated conductor of the called subscribers line to and through the bell at substation B to ground. The other conductor of the subscriber s line at the same time is grounded by way of ringing sequence switch contact 510 (13), and the tip of the calling plug 32 and corresponding spring of the sprlngjack 14. The relay 62 is so constructed, as by providing its core with a copper sheath, that it is irresponsive to the normal ringing current flow. When, however, the called subscriber takes his telephone receiver from its hook in response to the ringing of the bell, the increased current flow in the circuit causes the operation of the relay 62.

The winding of the relay 61 is included in thepreviously-traced path including the relay ,60, but is normally short-circuited' by the branch of the circuit extending serially through the back contact of the relay 62 and the left-hand back wntact of the relay-61. )Vhen the relay 62 is-energized by the response of the called subscriber, this short circuit is broken and the relay 61 is energized. "When the relay 61 operates, it breaks this short circuit at its own left-hand armature and back contact so as to keep the short circuit open independently of its control by the relay 62; and also, at its right-hand armature and front contact closes a path from battery including the resistance 64 in shunt of the path that extends from battery by way of the winding of the relay 60. The resistance 64 is of relatively low value as compared with the resistance of the relay 60, so that when the relay 61 operates, the current flow through the winding of the relay 60 is reduced to a point where the relay 60 releases its armatures. In doing so, the relay 60 interrupts, at its left-hand'armature and front contact, the path over which the ringing current is flowing to the connecting circuit and at its right-hand armature and back contact, and closes an energizing path for, the motor magnet of the ringing sequence switch 500 by way of the contact 503 (4 to 13) of that switch. The result, therefore, is that the ringing sequence switch moves out of position 13 andstops in position 16, its next resting position. In moving out of position 13, the ringing sequence switch interrupts at contacts 507 (12 to 13) the energizing circuit for the relay 61.

in position 16 of the ringing sequence switch, a circuit is closed that includes the calling supervisory relay 65, with battery, in series with the circuit of the called line; and as the called subscriber has taken his telephone receiver from its hook, the relay 65 is energized. In operating, the relay 65 closes the energizing circuit of the motor 58. This extinguishes the lamp and notifies the operator that the called subscriber has responded.

(hen the subscribers replace their telephone receivers at the end of their conversation, the deenergization of the answering supervisory relay 51 and calling supervisory relay 65 causes the associated supervisory lamps 47 and 58 to be illuminated, and the operator takes down the connection by re moving the plugs 31 and 32 from the springjacks in which they are inserted. The removal of the answering plug 31 deenergizes the associated relays 41 and 45, and the withdrawal of the calling plug 32 denergizes the associated relays 33 and 37. In

positions 2 to 17 of theringing sequence switch, a path exists from battery through the winding of relay 66, and'by way of contacts 512 (2 to 17) of the ringing sequence switch to the right-hand back contact of the relay 33, and also to the left-hand back contactof the relay 45. Therefore, when eitherpf the plugs 31 and 32 is withdrawn from its spring-jack, a pathto ground for the energization of the relay 66 is completed by Way of the back contact and armature contact 512 (2 to 17) and the right-hand" front contact and armature of relay 66. Bic

lay 66 in operating also closes a circuit that extends from battery through the motor magnet and contact 502 (2 to 17) of the ringing sequence switch, and left-hand front contact and armature of relay 66 to ground. As a result of the closure of this circuit, the ringing sequence switch 500 moves out of position 17 and comes to rest in its 101 normal osition.

It will be remembered that after the relay 42 became energized as a result of the insertion of the answering plug, its energization was maintained by two paths, one of which extended to ground from the lefthand winding of relay 42 by way-of the right-hand back contact and armature of relay 40 and right-hand front contact and armature of relay 45, and the other of which extended to ground by way of right-hand front contact and armature of the relay 33. As 'bothrelays 45 and--33 are released by the withdrawal of the answering plug and calling plug, respectively, both of these paths are broken and the relay 42 releases its armatures. In doing so a circuit is completed that extends from battery through the motor magnet and contact 102 (7 to 15) of the listening-key sequence switch and to ground by way of the right-hand back contact and armature of relay 42. When this.

happens, the listening-key sequence switch is moved from either of the positions 7 and 15 in which it may be standing, and is caused to return to its normal or 1 position. The withdrawal of both plugs, therefore, results in the restoration of the circuits of the special connecting cords S to their normal condition.

In order to illustrate other operative capabilities of the organization disclosed herein, it will now be assumed that the operator has attempted to establish a connection by means of the regular cord circuit C, has found that the called subscriber does not answer, and has been requested by the calling subscriber to call him when she is able to get the line that is being called. Tn this case, the operator after an interval tests the multiple spring-jack of the called line with the tip of the calling plug 32 of the special connecting circuit. If the line tests free, she inserts theplug 32 into the s ringjack. Under these circumstances, t e insertion of the calling plug does not bring about the application of ringing currentto the called line, for the reason that the circuit for moving the ringing sequence switch out of position 1, although closed at sequence switch contact 502 (1) and righthand front contact and armature of relay 37, is open at the right-hand front contact and armature of relay 41, the answering plug not being inserted. The operation of the rela- 37 resultant upon the insertion of the calling plug 32 closes a circuit that extends from battery by way of the left-hand winding of the relay 10 and the winding of the relay 43 in parallel, the right-hand back contact and armature of relay 4:1, and the. right-hand front contact and armature of relay 37 to ground. Relay 4:0 in operating closes a locking circuit for maintaining its energization by way of its left-hand front contact and armature and the left-hand armature and front contact of relay 37 to ground. it also closes another locking circuit for itself that extends from battery through the right-hand winding of relay all), and thence to ground by way of the inner and outer right-hand front contacts of relay l0 (closed together by the attraction of the right-hand armature of that relay), and, the right-hand front Contact and armature of relay 33 to ground. A branch path also ertends from the right-hand armature of re lay 10 to the right-hand front contact of the relay ie, and is completed to ground when the relay i5 is energized by the insertion of the answering plug 31. Thus, after relay ll) is initially energized by the insertion of the calling plug 32 at a time reoaeeo The effect of the energization of the relay l0 is to interrupt the path by which the insertion of the answering plug 31 and the operation of the relay 45 normally effects the initial energization of th relay 12, the interruption being at the right-hand back contact and armature of the relay l0. Therefore, if the callingp-lug 32 is inserted before the answering plug 31 is inserted, the relay l2 is not energized by the insertion of the answering plug and the listening-key sequence switch is not automatically moved out of its normal position and into its listening-in position 'Z.

Having inserted the calling plug 32 into the spring-jack of'the line that did not answer when connection was attempted by way of the regular connecting circuit C, the operator then tests the multiple spring-jack of the calling line by touching it with the tip of the answering plug 31. lf she finds that the calling line is free, she inserts the answering plug 31 into the spring-jack. The resultant operation of the relay .15, as has just been pointed out, does not operate the listening-key sequence switchto bring the operators telephone set into connection with the circuit. Relay 11 in operating, however, completes at its right-hand front contact and armature the circuit for moving the ringing sequence switch 500 out of position 1, this circuit being already closed at sequence switch contact 502 (1) and right-hand front contact of relay 3?.

, In the operation described in the preceding part of this specification, the movement of the ringing sequence switch into position 2 caused the listening sequence switch to move out of position "7, and the movement of to control the ringing sequence switch or to be controlled by it. This condition is provided for through the agency of the relay (l3, which, it will be remembered, has its winding in parallel with the left-hand winding of the relay 1-0, and which therefore was energized when the calling plug was inserted, and remains energized over the locking circuit by way of the left-hand front contact and armature of relay'elO as long as the calling plug 32 is in its spring jack. Relay as in operating opens at its right-hand back contact and armature the path over which Mill the listening sequence switch is normally moved out of position 7 when the ringing sequence switch 500 moves into position 2. It also closes at its left-hand front contact and armature an energizing circuit for the motor magnet of ringing sequence switch 500 byway of contact 503 (2) of thatsequence switch. Therefore, when the ringing sequence switch is moved to position 2 as a result of the insertion of the answering plug, it is moved through that position and into its ringing position, although the listening sequence switch is not energized to move its cams. Thus the insertion of the calling plug before the insertion of the answering plug causes the called subscribers line to be rung without connecting the op erators telephone with the circuit, a result that is of advantage, inasmuch as the operatOIf is thus enabled to proceed with the establishment of this special connection without interfering with her regular work.

The calling subscriber is not rung until the called subscriber answers. The response of the called subscriber is indicated by the extinguishing of the ringing lamp 55 and the calling supervisory lamp 58, both of which are lighted while the ringing sequence switch is in its ringing position. The operator then brings her telephone into connection with the circuit by pressing the listening-in key 67. This closes a circuit that extends from battery through the right-hand winding of relay 42, listening sequence switch contact 404. (l), and to ground by way of the co tact and switch spring of the listening-in key. Relay 42 in operating closes a circuit that extends from battery through the motor magnet and contact 402 (l) of the listening sequence switch, inner and outer left-hand front contacts of the relay 49. (closed together by the attraction of the left-hand armature of that relay), and thence to ground over two paths, one of which extends by way of the inner front contact and right-hand armature of relay 40. and the right-hand front contact and arma ture of relay 45, and the other of which extends by way of right-hand front contact and armature of relay 33. Relay 42 in operating also closes a locking circuit for itself by way of its left-hand winding and its lefthand garmature and front contact and the two branch paths to ground just traced. Therefore, after the relay 42 has once been operated by the pressing of the listening-in key 67, it remains operated as long as either plug is in its spring-jack, and prevents the listening sequence switch from stopping in its normal or 1 position.

The movement of the listening sequence switch to position 7 in the manner just described, puts the operator into communication with the called subscriber; and she tells him that he being called and asks him to hold the line. She then presses the ringback key 160 included in her telephone circuit loop. This applies ringing current to the calling subscribers line and rings the bell at the calling station. At the same time, the operator may operate the splitting key so as to spread the switch spring 69 and leave the switch springs 68 in their normal position. The result of this is to disconnect the talking strandsof the callingcord from the corresponding windings of the repeating coil and connect them instead with the windings of the retardation coil 71. This destroys the inductive or talking connection between the calling half and the answering half of the connecting circuit, and

.leaves the operators telephone connected with the answering half, so that when the calling subscriber'responds to the ringing of his bell, the operator may talk to him without the conversation being overheard by the called subscriber who is now waiting at his telephone. WVhen the calling subscriber answers, the operator tells him that she has obtained the connection, and then puts the two subscribers into communication by moving the splitting key to return the set of switch sfprin'gs 69 to their normal position.

If he ore the operator puts the two subscri'bers into communication she wishes to speak to the called subscriber without be ing overheard by the calling subscriber, she operates the splitting key so as to spread the switch springsof the set 68 without moving the switch springs of the set 69 from their normal position. The result of this is to disconnect the talking strands of the answering cord from the corresponding windings of the repeatin coil 70 and connect them instead with t e windings of the retardation coil 71, thus destroying the talking connection between the two halves of the connecting circuit. At the same time, the spreading of the switch springs 68 closes a circuit that extends from battery through the winding ,of'the relay 57, listening sequence" switch, contact 413 (5 to 7), and the lower contact and switch spring of the set 68 to ground. Relay .57 in operating disconnects the operators telephone set from the loop circuit-controlled by the listening sequence switch cams 408, 409, 410 and 411, associated with the answering half of the cord circuit, and connects it instead, by way of the listening sequence switch "cams 412 (7) and 41 (7 with the calling half of the connecting circuit. The operators telephone set is thus disconnected from the answering cord and is connected with the calling cord of the circuit.

After establishing the connection between the two subscribers, the operator disconnects her telephone set from the circuit by pressing the master listening-out key 72. Thiscloses a circuit for the energization of the motor magnet of the listening sequence switch by way of contact 403 (7) of that switch, and contacts of the listening-out key 72, and the listening switch thereupon moves to position 15, the-listening-out position. If the operator again should have occasion to connect her telephone set "with the circuit, she may do this by pressing the listening-in key 67. This closes the energizing circuit of the motor magnet by way of contact 404 (15) withdrawal of the answering plug and calling plug, the consequent dee'nergization of relays 41 and 45 associated with the answering cord and relays 33 and 37 associated with the calling cord, opening the locking circuits of the relays 40, 42 and 43 and closing the circuits for the return of the listening sequence switch and the ringing sequence switch to normal, as already described.

There is a common connection from the contact-402 (7) of all of the listening sequence switchesv of the operators position to ground by way of common conductor 421 and the contacts 415 (2 to 6) of all of these listening sequence switches. T he common conductor 421, as shown in Fig. 2, is also multlpled to contacts of-sequence switch springs 320 of all the sequence switches 300 of the regular connecting cords C. As a result of this connection, any listening sequence switch 1n moving to its listening-in position 7, applies a ground for the energizationof the motor magnet of any other listening sequence switch that may be standing in position 7', so that the connection of the operators telephone set with any of the circuits causes the automatic disconnection of the set from any other circuit with which at the time it. may be connected.

Another one of the special circumstances under which the operator may use the special connecting circuit S, is when she has accidentally made connection with and sig-' naled the wrong line on a call that has reached her over the regular connecting circuit C. In this case, upon discovering her mistake, she brings her telephone set into connection with the connecting clrcuit C, withdraws the plug 170 from the springjack in which it was mistakenly inserted, and inserts the calling plug 32 of the special circuit S into the spring-jack from which the plug 170 has been withdrawn. She then proceeds to establish the proper connection by way of the regular connecting circuit C,

the special connecting circuit remaining -400 into position 7 to bring her. telephone set into connection with the connecting circuit S. As the answering plug 31 of the special circuit is not inserted, in a springjack, the energizing circuit for the motor. magnet of the ringing sequence "switch 500 by way of the cam 502 (l) is not completed, and the ringing sequence switch remainsin position 1. In .posltion 1, the talking 'conductors of the connecting circuit are closed at contacts 510 (1) and 511 (1) ofthe ringing sequence switch, and-the. operator is therefore in telephonic communication with the subscriber who has been falsely signaled, and may excuse thecall. When'the relay 42 was energized as the result of the depression ofthe listening-in key 67 it locked up b way of its left-hand winding, its lefthan armature. and' front contact, and the right-hand front contactand armature of relay 33 to ground, When the operator withdraws the calling plug 32 after excusing the false call, the relay 42 1s deiinergized, and

closes at its-right-hand armature andbackcontact a circuit by way of listening sequence cam 402 (7 to 15),which disconnects the operators telephone from the circuit and restores the listening sequence switch to position 1.

In addition to the foregoing and other special uses for which it is adapted, the spe cial cord circuit is adapted to be used as an A-o rators cord circuit in answering calls and'directly' establishing connections in the ordinary way. Such use ma be illustrated by assuming that the line re ays 12 and 12 of the two telephone line circuits shown act to cause the illumination of answering lamps 15 and 15 located in association, respectively with the spring-jacks 14 and 14 of those lines, and shown connected with the front contacts of their respective relays by dotted line circuits. With the arrangement assumed, when the telephone receiver is taken from its switchhook at either of the stations A and B, the corresponding line replug 31 of the connecting circuit .S into the associated spring-jack. -The resultant energ zationof the relay 45 causes relay 42 to operate to move the listening sequence switch 400 into its listening-in position 7, thus automatically bringing the operators tele phone set into connection with the circuit. At the same time the lamp is intermittently energized to give a flashing call signal, the answering supervisory lamp 47 remaining dark.

When the operator has learned the number of the line with which connection is desired, she inserts the calling plug 32 of the connecting circuit S into the spring-jack of that line, after testing the sleeve of the spring-jack with the tip of the plug 32 to ascertain whether or not the line isfree for connection. The insertion of the calling plug 32 actuates the relay 37 to complete the closure of the circuit that energizes the motor magnet of the ringing sequence switchand moves it out of position 1. When it reaches position 2, the ringing sequence switch moves the listening sequence switch out of position 7 to disconnect the operators telephone apparatus from the circuit; and in moving out of position 7, the listening sequence switch moves the ringing sequence switch out of position 2, from which position the ringing sequenceswitch then moves to position 13 and efiects the application of ringing current to the called subscribers line. When the called subscriber responds, the ringing sequence switch is moved to position 16, and then, through the actuation of the calling supervisory relay 65, is moved to the talking position 17, in which the conversational connection between the'two subscribers is established. The lamp 55, which changed its flashing'call signal to a steady illumination when the listening sequence switch moved. out of position 7 and'the ringing sequence switch moved into position 3, is extinguished when the called subscriber answers and the ringing sequence switch is moved out of position 16.

During the continuance of the connection, the operator may connect or disconnect her telephone apparatus with the connecting circuit by operating the listening-in-key 67 or the listening-out key 72; or, if for any reason it becomes necessary, she may talk to either subscriber and exclude the other by operating one or the other of the set of switch springs 68 and 69 of the splitting key. When the subscribers hang up their telephone receivers at the end of the conversation, the supervisory lamps 47 and 58 are lighted, and the operator takes down the connection by withdrawing the plugs 31 and 32. The withdrawal of these plugs restores all the apparatus to its normal condition in a manner that has hereinbefore been described.

WVh-at is claimed is:

The combination with a connecting circu it having an answering plug and acalling plug, of operators telephone apparatus,

control said electromagnetic witch.

The combination with a plurality of telephone lines, of a connecting circuit provided with connecting switches for interconnecting said telephone lines, operators t'elephone apparatus, an electromagnetic switch for connecting said telephone apparatus to the connecting circuit, and a relay under the joint control of said connecting switches for rendering said electromagnetic switch either operative or inoperative dependent upon the sequence in which said connecting switches are closed.

3. The combination with a plurality of telephone, lines, of a plug-tenninated connecting circuit forinterconnecting said lines, operators telephone apparatus, an electromagnetic switch controlling the association of said telephone apparatus with said connecting circuit, said switch having a normal position, a listening-in position and a. listening-out position, means actuated by the insertion of the answering plug for moving said switch out of its normal position and into its listening-in position, means actuated "by the insertion of the calling plug prior to the insertion of the answering plug for preventing such control of said switch by said answering lug, and means for preventing the return 0 said electromagnetic switch to its normal position while either of said plugs is inserted.

4:. The combination with a plurality of telephone lines, of a circuit for interconmeeting the same, said circuit being provided with an answering connection switch and a calling connection switch, operators telephone apparatus, a sequence switch for controlling the connection of' said telephone apparatus Withsaid connecting circuit, said switch having a normal position, a listeningin position, and a listening-out position, a

listening-in key, means actuated by the closure of said answering connection switch or by the operation of said listening-in key for moving. said sequence switch from its normal to its listening-in position, means for moving said sequence switch from its listening-1n to its llstenlng-out positldn. and

means actuated by the opening of both of said connection switches for returning said sequence switch to its normal position.

5. The combination with a plurality of telephone lines, of a plug-terminated circuit for interconnecting the same,'operators telephone apparatus, an electromagneticlistening switch for controlling the connection of said telephone apparatus withsaid connecting circuit, means actuated by the insertion of the answering plug of said pair before the calling plug is inserted for operating said switch to connect said telephone apparatus with the circuit, means controlled jointly by both plugs actuated by the insertion of the calling plug before the insertion ofthe answering plug for preventing the insertion of the answering plug from actuating s'a-id switch to connect the telephone apparatus, and manually operated switch mechanism operative when either plug is inserted for controlling the connecting and disconnecting operation of said listening switch.

6. The combination with a plurality of telephone lines, of a circuit for interconnecting the same, said circuit being provided with an answering connection switch and a calling connection switch, operators tele: phone apparatus, means actuated by the closure of the answering connection switch for connecting said telephone apparatus with the connecting circuit, means actuated by the closure of the calling connection switch. for disconnecting said telephone apparatus from the circuit, independent means tor controlling the connection of said telephone apparatus with and its disconnection from said connecting circuit, and means actuated by the closure of the calling connection switch before the closure of the answering connection switch for making said independent means operative and preventing the closure of the answering connection switch from causing the connection of said telephone apparatus with the circuit.

7. The combination with a plurality of telephone lines, of a circuit for interconnecting the same, said circuit being provided with an answering connection switch and a calling connection switch, operators telephone apparatus, means actuated by the closure of the answering connection switch for connecting said telephone apparatus with the connecting circuit, means actuated by the closure of the calling connection switch for disconnecting said telephone apparatus from the circuit, independent means for controlling the connection of said telephone apparatus with and its disconnection from said connecting circuit, and means made operative by the closure of the calling connection switch before the closure of the answering connection switch for preventing the closure of the calling connection switch from causing the disconnection of said telephone apparatus from the circuit.

8 The combination with a plurality of telephone lines, of a circuit for interconnecting the same, said circuit being provided with an answering connection switgh and a. calling connection switch, operators tele plione apparatus, an electromagnetic switch controlling the connection or said telephone apparatus with said circuit, a listening-in hey, means actpated by the closure of said aaoaeco calling connection switch and the operation of said. listening-in key for actuating said electromagnetic switch to connect the operators telephone apparatus with the circuit, and means made operative by the opening of said calling connection switch for actuating said electromagnetic switch to disconnect the operators telephone apparatus from the circuit. 4 I

9.-T he combination with a plurality of telephone lines, of a circuit for interconnecting the same, said circuit being provided with an answering connection switch and a calling connection switch, opcrators telephone apparatus, an electromagnetic switch controlling the connection of said telephone apparatus with said circuit, a listening-in key, means actuated by the closure of said calling connection switch. and the operation of said listeningrin key for actuating said electromagnetic switchto connect the operators telephone apparatus with the circuit, a listening-out key, and means made operative either by the opening of said calling connection switch or by the operation of said listening-out key for actuating said electromagnetic switch to disconnect the operators telephone apparatus from the circuit.

10. The combination with a plurality of lines, of a circuit for interconnecting the same, said circuit having an answerin connection switch and a calling connection switch, operators telephone apparatus, a sequence switch for connecting said telephone apparatus with and disconnecting it from said connecting circuit, manually operated switching mechanism, and means made operative by the closure off either of said con nection switches for placing said sequence switch under the control of said manually operated switching mechanism.

11. The combination with a plurality 0t" telephone lines, of a connecting circuit provided with an answering plug and a calling plug, operators telephone apparatus, an electromagnetic switch controlling the connection and disconnection of said telephone apparatus with said connecting circuit, manual switching mechanism for controlling said electromagnetic switch when either plug is inserted, and a relay under the joint control of said answering plug and said calling plug for automatically controlling said electromagnetic switch when the answering plug is inserted before the calling plus".

12. The combination s. with a plurality of telephone lines, of a circuit for interconnecting the same, said circuit being provided with an answering connection and a calling connection switch, an electrzmiagnetic' listening switch, an electromagnetic ringing switch, means made operative when the answering connection switch is closed first for rendering the operation of said ringing swit hsubject to the movement of said lls'ten ng switch, and' ineans made operative when the calling commotion switch is closed first for rendering said ringing switch independent of control by said listeningswitch:

l3. The'combination with a plurality of telephone l1nes,"of* a circuit for intercon necting the same, said circuitbeing provided with an answering plug and a'calling plug, operators telephone apparatus and anelectroinagnetic listenin switch for con trolling the connectionof the sanie with said connecting'circiiit; afs' ource of ringing current and-a electromagnetic ring ng switch -for controlling the connection of, the same with said connecting circuit; means m p ive y the i itie Q a d answering plug fir-stiff r operating listening switch and rendering the ove ment of saidringing to the movement '0':- said' "listening 'fs'witch,' means render d operative bj the insertion of said callingplngfirst for rendering'the movement'ofsa d ringing switch i'rrdependent of the movement of said listening switch.

5 he c mb a i ith "a qnaec iiis circuit having an answering connection.-

switch and a calling cunnection switch, of

operators telephone apparatus'and' an elec tromagnetic listening switch for connecting the same with the c1rcuit, a' source of ring ing current and an electromagnetic ringing switch for'connecting sa'id s'ourc'e with the circuit, reciprocal controlling means between said listening switchan said ringing switch made operative by the closure of said answering connection switch first, and

4 means made operative by the closure of said calling connection switchffirst for making said reciprocal controlling means inoperative and rendering said ringing and listening switches. operable independently of each other.

15. The combination with a plurality of telephone lines, f a connecting circuit having an answering plug. and a callinglu operators telephone apparatus an P a electromagnetic listening switch for controllin the connection and disconnection of said te ephone apparatus with said connecting circuitjmeans under the joint'co'ntrol of said answering plug and said calling plug, and "operative onl if the answering plug is inserted before t e calling plug, for controlling the operation of said listening switch, a source of ringing current, a in switch for connecting the same wit said connecting circuit,- means under the joint control of both of said plugs and said listening switch for actuating said rmgmg: switch, and means made operative when said calling plug is inserted before said 15 answering plug for depriving said listening switch 101?- control over said ringing switch.

. 16.'The combination with a plurality of telephone lines, of'a plug-terminated connecting circuit for interconnecting the same, operators telephone apparatus and a listening sequence switch for controlling the connection of the same with said connecting circuit, a source of ringing current and a ringing sequence switch for controlling the .appl i'ca'tionfof ringing current from said listening sequence s normal listening-in tor mevjmg' 'said' listening sequence" to its listening out' posi-v tib e a the listening ted b said ment I switc t r m iii s'th rins ng s i h b' l nsi pe tion, means a uated by the responseioi the calied subscriber for moving the ringing seque'no'e switcli to its talkingposition; means actuatedby-t'he withdrawal of either of said plugs for moving said ringing sequence a switch to its normal position, andmeans actuated by thewithdrawal of both of said plugs for nioving said listening sequence switch-to it's normal position.

17. The combination with a plurality of telephone lines, of a plug-terminated Circuit for interconnecting the same, operators telephone apparatus, a'switchlfor controlling the connection of the same with'said "circuit, a source'of ringing current, an elec tromagnetic'switch for controlling the application oi ringing current" from said actuated by the insertipn of source to said connecting circuit and 4.

means operatedby the insertion of both plugs and the movement of said first men-.

tioned switch for actuating said electromagnetic switch to apply ringing current. 18. The combination with a plurality of telephone lines," of a plug terminated cir-v cu'it for interconnecting the same, operators telephone apparatus, a switch for controlling the connection of the same with said circuit, a'source of ringing current, an electromagnetic switch for controlling the application of ringing current from saidsource tosaid connecting circuit, means operated by the insertion of plugsand the movement of said firstm'entioned switch for. actuating said electromagnetic switch to apply ringing current, and means actuated by the withdrawal of either plug for actuating said switch to disconnect ringing current.

19. The combination with a plurality of connecting the same, said-cord circuit having air-answering .plug and a calling plug;

a source of ringing current, a sequence switch for controlling the application of ringing current from said course "to said connecting circuit, means made operative by the insertion of both plugs. for moving said sequence switch out of its normal position and into its ringing position where it applies ringing current to the connecting scriber for moving said sequence switch to disconnect ringing current from the circuit 15 and establish. the talkingconnection, and meansactuated by the withdrawal of either plug for returning said sequence switch to normaL- In witness whereof; I hereunto subscribe 20 my name this 13th day of July A. D.,'19l 7.

-. RALPH L. QUASS. 

